# 1st law of Thermodynamics Worksheet

```1st law of Thermodynamics Worksheet
Name: ___________________________
Show your work and use significant figures.
1) Calculate ∆E for each of the following cases:
a. q = + 51 kJ, w = - 15 kJ
b. q = + 100. kJ, w = - 65 kJ
c. q = - 65 kJ, w = - 20 kJ
d. In which of these cases does the system do work on the surroundings?
2) Calculate ∆E for each of the following:
a. q = - 47 kJ, w = + 88 kJ
b. q = + 82 kJ, w = + 47 kJ
c. q = + 47 kJ, w = 0
d. In which of these cases do the surroundings do work on the system?
3) A system releases 125 kJ of heat while 104 kJ of work is done on the system. Calculate
the change in internal energy (in kJ).
4) A system undergoes a process consisting of the following two steps:
Step 1: The system absorbs 73 J of heat while 35 J of work is done on it.
Step 2: The system absorbs 35 J of heat while performing 72 J of work.
Calculate the change in internal energy for the overall process (in J).
5) The volume of an ideal gas is decreased from 5.0 L to 5.0 mL at constant pressure of 2.0 atm.
Calculate the work associated with this process (in J). WATCH YOUR UNITS!!!
6) The reaction of nitrogen with hydrogen to make ammonia is
N2 (g) + 3H2 (g)  2HN3 (g)
ΔH = -92.2 kJ
What is the value of ΔE (in kJ) if the reaction is carried out at a constant pressure of 40.0 atm
and the volume change is -1.12L? WATCH YOUR UNITS!!!
7) The reaction between hydrogen and oxygen to yield water vapor is
2H2 (g) + O2 (g)  2H2O (g)
ΔH = -484 kJ
How much PV work is done (in J) and what is the value of ΔE (in kJ) for the reaction of 0.50
mole H2 with 0.25 mol of O2 at atmospheric pressure if the volume change is -5.6L? WATCH